The pyrotechnic mechanism that wasn't, and other tidbits from a lawsuit filed in February against most of the world's power tool companies.

This is from the PTI patent. Figure 1 shows the blade retraction system under normal operating conditions. Figure 2 is a cutaway of the blade retraction mechanism. A cylinder (66) fits inside a cylinder bore (64). When the spinning blade touches flesh a capacitor sends a burst of high amperage electricity through a wire (78) and into a pin (74) that causes a .22 calibre cartridge (68) to fire.

Figure 3 shows the blade as it begins to retract after the cartridge is fired. Figure 4 shows the firing mechanism (60) at the same point in time: The gas generated the cartridge (68) has forced the cylinder (66) out of the bore (64) and driven the hammer (82) into an anvil (102 fig 3) that is a connected to a curved arm (20). The arm is connected to the saw’s arbor and is beginning to pull it below the table.

The defendants listed on the first page of the complaint are a who’s who of power tool makers that sell table saws in the U.S. Chang Type Industrial owns Delta, having purchased it from SB&D in 2011. Emerson Electric is listed because it owns the Ridgid brand. It’s unclear why Milwaukee is there; it doesn’t even make table saws. Pentair, which sold its power tool business (Porter-Cable and Delta) to Black & Decker in 2004, has been released from the suit by the judge. Techtronic (TTi) is on the list because it owns Ryobi (and also Milwaukee).

This is from page 20 and 21 of the complaint filed by SawStop and SD3. What’s interesting is PTI’s estimate of the annual number of table saws shipped between 2006 and 2010. If those figures are correct, sales averaged 700,000 units per year. Multiply that by the licensing fee SawStop would receive if its technology was used on each of those saws (SawStop has said $50 each; PTI has said $200+) and you can see why the two sides think this is worth fighting about.

Page 22 of the complaint contains the Consumer Product Safety Commission’s estimate of the annual cost of table saw injuries: $2.36 billion per year. It’s worth noting that this number includes the cost of medical treatment, lost work time, legal and administrative fees, AND the “pain and suffering” that would be awarded if every table saw injury resulted in a lawsuit and the injured party won. More to follow…

In 2012 PTI commented (see paragraph 3; page 21) on the CPSC’s proposed rule, stating that 80% of the estimated cost (ICM) of $2.36 billion per year is pain and suffering. According to PTI, the inclusion of legal fees and pain and suffering has caused the CPSC to overstate the cost to society of table saw injuries.

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A few weeks back I stumbled across a story about the arguments being made in a lawsuit between SawStop and most of the world's power tool companies. After a bit of online searching I found the original complaint, a 40-page document that was filed in February at the U.S. District Court in the Eastern District of Virginia. The plaintiffs (SawStop and its parent company SD3) claim the defendants (most of the world's power tool companies) engaged in a group boycott of SawStop technology, violated the Sherman Antitrust Act by collectively refusing to license that technology, and fraudulently concealed a conspiracy to do all of the above. They also accuse the defendants of conspiring to influence and corrupt UL by convincing that organization not to incorporate SawStop technology into its safety standards and to change UL standards to limit competition in table saw blade guards (SawStop's then current guard did not comply with the new standard and they were forced to redesign it.)

At this point the complaints leveled by SawStop and SD3 are unproven allegations. It will be up to Judge Claude Hilton of the United States District Court Eastern District of Virginia and a jury—if one is empaneled—to decide whether or not any of the plaintiff's claims have merit.

The preliminaries are underway and according to a report in Law360, on April 10 the defendants' attorneys filed a motion to dismiss, claiming the collusion charge was baseless because "numerous defendants made offers to license the SawStop technology months after the purported October 2001 agreement to boycott the plaintiff's technology". The defendants' legal team slammed SawStop, saying it is not the champion of consumer welfare it claims to be and that the suit is an effort to force rivals to license its technology on unfavorable terms and prevent it from having to compete with less expensive alternatives to its technology.

That last bit, about less expensive alternatives, has to do with a safety system that has never been offered to the tool-buying public. The system—which consists of electronics and a pyrotechnic drop mechanism—was jointly developed under the auspices of the Power Tool Institute (PTI), a trade group that represents many of the world's power tool companies. It works like this: when the saw's electronics sense flesh (or some other conductive material) they fire a .22 caliber blank and use the resulting gas pressure to retract the blade below the table in a matter of milliseconds—fast enough to prevent serious injury to the person whose flesh touched the blade (see slideshow). According to PTI, the blade isn't damaged and for the cost of a shell (the kind used in powder actuated fastening tools) the mechanism can be reset and the saw put back into action. Activating the SawStop mechanism destroys the blade and a $70-90 cartridge.

PTI received a U.S. patent (7,628,101) for its safety system in 2009 but claims actions by SawStop have prevented its use. In comments submitted (see page 11) to the Consumer Product Safety Commission (CPSC) in March 2012, the PTI said that when SawStop learned of the pyrotechnic drop mechanism it "amended one of its then-pending patent applications to purportedly cover any table saw that, instead of application of a blade braking system, would retract the blade rapidly within 14 milliseconds –using any retraction technique after detecting contact." That application was accepted by the U.S. patent office—effectively nixing any competing system that relies on fast retraction of the blade. The power tool companies could make use of the PTI safety system but it would mean engaging in costly patent infringement litigation with no guarantee they'd prevail.

It will be interesting to see how this all plays out. In the meantime, you might want to check out the slideshow on the left—which contains patent drawings of PTI's pyrotechnic safety device and some interesting tidbits from SawStop's complaint. If you're a table saw user and have an opinion about SawStop, PTI, or the lawsuit discussed in this story, feel free to share in the comments section below.